Laser-induced fluorescence (LIF) images have been collected through a fiber optic endoscope in vitro, and have been usedto detect dysplasia in colon with high contrast and resolution. Colonic mucosa was illuminated with 100 mW of near-UV excitation, consisting primarily of wavelengths 351 and 364 nm. The endogenous fluorescence response between 400 and 650 nm was detected by an intensified CID camera. Adenomatous polyps appeared on the LIF image to be less intense than normal by a factor of 3-4. Colon samples were obtained from surgical resections of familial adenomatous polyposis patients, and specimens with dimensions of 3 x 2 cm2 were illuminated through a 600 mm fused silica fiber by an argon-ion laser. A cutoff filter at 400 nm was placed in front of the endoscope to block the excitation light. The images were processed by subtracting out local average values and thresholding, and regions of the LIF image identified as dysplastic were verified by histology. The contrast between normal and diseased tissue provides potential for LIF to be used as an adjunct to conventional tissue.